Rework and stripping of complex patterning layers using chemical mechanical polishing

ABSTRACT

A method utilizing a chemical mechanical polishing process to remove a patterned material stack comprising at least one pattern transfer layer and a template layer during a rework process or during a post pattern transfer cleaning process is provided. The pattern in the patterned material stack is formed by pattern transfer of a directed self-assembly pattern generated from microphase separation of a self-assembly material.

BACKGROUND

The present disclosure relates to semiconductor device fabrication and,more particularly, to a method of reworking and stripping patterninglayers using a chemical mechanical polishing process.

Pattern generation using directed self-assembly (DSA) of polymericmaterials is a promising candidate to extend current lithography insub-20 nm technologies for integrated circuit (IC) manufacture. In atypical DSA process, microphase separation of a block copolymer that isguided by an external field, either chemistry or topography, results ina well-defined pattern with sub-photolithographic resolution.Subsequently, one of the domains is selectively removed, leaving theother domain to serve as a lithographic mask for pattern transfer tounderlying resist layers and eventually to the semiconductor devices.However, during the pattern transfer processes, formation of the patternin the patterning layers may fail, leading to defects in the patternsubsequently formed in the semiconductor devices. Once failure occurs,the patterning layers need to be removed by a rework process. The reworkprocess can include a dry etching process such as an ashing processusing an oxygen plasma, or a wet cleaning process using an organicstripper solution. However, in the case of the DSA process, exposedsurfaces of the patterning layers might be modified by residues of theblock copolymer which makes them difficult to remove with conventionalcleaning processes. Therefore, new processing methods for removingpatterning layers are needed in the DSA pattern transfer process.

SUMMARY

The present disclosure provides a method utilizing a chemical mechanicalpolishing process (CMP) to remove a patterned material stack comprisingat least one pattern transfer layer and a template layer during a reworkprocess or during a post pattern transfer cleaning process. The patternin the patterned material stack is formed by pattern transfer of adirected self-assembly pattern generated from microphase separation of aself-assembly material.

In one aspect of the present disclosure, a method for making asemiconductor structure is provided. The method includes first providinga hardmask layer on an uppermost surface of a substrate. A materialstack is then formed on the hardmask layer. The material stack includesat least one pattern transfer layer and a template layer present on thepattern transfer layer. After forming at least one opening in thetemplate layer, a patterned structure is formed in the opening. Thepatterned structure comprises a first self-assembled region and a secondself-assembled region. The second self-assembled region is removed toprovide a first pattern. The first pattern is defined by the firstself-assembled region. Next, the first pattern is transferred into theat least one pattern transfer layer to provide a second pattern. Afterremoving the first self-assembled region, residues of the firstself-assembled region, remaining portions of the template layer,remaining portions of the at least one pattern transfer layer areremoved from the substrate by performing a chemical mechanical polishing(CMP) process.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view of an exemplary structure after forminga hardmask layer and a material stack on a substrate according to anembodiment of the present disclosure.

FIG. 2 is a cross-sectional view of the exemplary structure of FIG. 1after forming an opening in a template layer of the material stack.

FIG. 3 is a cross-sectional view of the exemplary structure of FIG. 2after depositing a self-assembly material in the opening.

FIG. 4 is a cross-sectional view of the exemplary structure of FIG. 3after forming a first self-assembled region and a second self-assembledregion by microphase separation of the self-assembly material.

FIG. 5 is a cross-sectional view of the exemplary structure of FIG. 4after removing the second self-assembled region to provide a firstpattern.

FIG. 6 is a cross-sectional view of the exemplary structure of FIG. 5after forming a second pattern in the material stack to provide apatterned material stack.

FIG. 7 is a cross-sectional view of the exemplary structure of FIG. 6after removing the first self-assembled region from the patternedmaterial stack and leaving residues on exposed surfaces of the patternedmaterial stack.

FIG. 8 is a cross-sectional view of the exemplary structure of FIG. 7after removing residues of the first self-assembled region and thepatterned material stack form the hardmask layer using a chemicalmechanical polishing (CMP) process.

FIGS. 9A and 9B are scanning electron micrograph (SEM) images of theexemplary structure of FIG. 8 before (FIG. 9A) and after (FIG. 9B) theCMP process.

FIG. 10 is a cross-sectional view of the exemplary structure of FIG. 7after transferring the second pattern into the hardmask layer.

FIG. 11 is a cross-sectional view of the exemplary structure of 10 afterremoving the first self-assembled region from the patterned materialstack and hardmask layer and leaving residues on exposed surfaces of thepatterned material stack and the patterned hardmask layer

FIG. 12 is a cross-sectional view of the exemplary structure of 10 afterremoving residues of the first self-assembled region and the patternedmaterial stack from the patterned hardmask layer using a CMP process.

DETAILED DESCRIPTION

The present disclosure will now be described in greater detail byreferring to the following discussion and drawings that accompany thepresent disclosure. It is noted that the drawings of the presentdisclosure are provided for illustrative purposes only and, as such, thedrawings are not drawn to scale. It is also noted that like andcorresponding elements are referred to by like reference numerals.

In the following description, numerous specific details are set forth,such as particular structures, components, materials, dimensions,processing steps and techniques, in order to provide an understanding ofthe various embodiments of the present disclosure. However, it will beappreciated by one of ordinary skill in the art that the variousembodiments of the present disclosure may be practiced without thesespecific details. In other instances, well-known structures orprocessing steps have not been described in detail in order to avoidobscuring the present disclosure.

Referring to FIG. 1, there is illustrated an exemplary structure thatcan be employed in an embodiment of the present disclosure.Specifically, the exemplary structure includes a substrate 10, ahardmask layer 20L present on an uppermost surface of the substrate 10and a material stack 22 present on an upper surface of the hardmasklayer 20L. The material stack 22 typically comprises at least onepattern transfer layer and a template layer 28L present on the at leastone pattern transfer layer. In one embodiment, at least one patterntransfer layer comprises, from bottom to top, an organic planarizationlayer (OPL) 24L and an antireflective coating (ARC) layer 26L. Layers inthe material stack 22 are collectively referred to as the patterninglayer.

The substrate 10 in the present disclosure can be any substrateconventionally used in processes involving a photoresist. For example,the substrate 10 can be silicon, silicon oxide, aluminum, aluminumoxide, gallium arsenide, ceramic, quartz, copper or any combinationthereof including multilayers. The substrate 10 can include one or moresemiconductor layers or structures and can include active or operableportions of semiconductor devices.

The hardmask layer 20L provided on the topmost surface of the substrate10 can include an oxide, nitride, oxynitride or any combination thereofincluding multilayers. Typically, the hardmask layer 20L is an oxidesuch as silicon oxide or a nitride such as titanium nitride. Thehardmask layer 20L can be formed by conventional deposition processes,such as, for example chemical vapor deposition (CVD), plasma-enhancedCVD (PECVD), physical vapor deposition (PVD) or atomic layer deposition(ALD). The thickness of the hardmask layer 20L can be from 5 nm to 50nm, although lesser and greater thicknesses can also be employed.

The OPL 24L can be formed on the upper surface of the hardmask layer20L. The OPL 24L can include near-frictionless carbon (NFC) material,diamond-like carbon, polyarylene ether or polyimide.

The OPL 24L can be formed utilizing any conventional deposition processincluding, for example, chemical vapor deposition (CVD), plasma enhancedchemical vapor deposition (PECVD), evaporation, spin coating and dipcoating. The thickness of the OPL 24L may vary depending on the materialas well as the deposition technique used in forming the OPL 24L. The OPL24L can have a thickness from 50 nm to 500 nm, although lesser andgreater thicknesses can also be employed. In one embodiment of thepresent disclosure, the OPL 24L has a thickness about 135 nm.

The ARC layer 26L can be formed on the upper surface of the OPL layer24L. The ARC layer 26L can include any ARC conventionally used inprocesses involving a photoresist. In one embodiment, the ARC layer 26Lis a silicon-containing ARC (SiARC) layer having a Si-content of about43%. The ARC layer 26L can be formed by spin coating, spray coating, dipcoating or PECVD. The thickness of the ARC layer 26L can be from 10 nmto 50 nm, although lesser and greater thicknesses can also be employed.In one embodiment of the present disclosure, the ARC layer 26L has athickness about 20 nm.

The template layer 28L can be formed on the upper surface of the ARClayer 26L. The template layer 28L can include any conventional organicphotoresist material, such as, for example, polymethacrylates andpolyesters. The template layer 28L can be a single layer or a multilayerstructure. In one embodiment, the template layer 28L has a multilayerstructure including a vertical stack of a lower OPL and an upper ARClayer. In one embodiment, the lower OPL has a thickness about 50 nm andthe upper ARC layer is a SiARC layer having a thickness about 30 nm.

The template layer 28L can be formed utilizing any conventionaldeposition process including, but not limited to, CVD, PECVD,evaporation, spin coating and dip coating. The thickness of the templatelayer 28L can be from 10 nm to 300 nm, although lesser or greaterthicknesses can also be employed.

Referring to FIG. 2, the template layer 28L is patterned to provide atleast one opening 30. The topography of the at least one opening 30 canguide the alignment of a self-assembly material that will be depositedwithin the opening 30 in the subsequent process.

The at least one opening 30 can be formed utilizing conventionallithography and etching. The lithographic step includes applying aphotoresist layer (not shown) atop the template layer 28L utilizing aconventional deposition process, such as, for example, CVD, PECVD andspin coating. Following formation of the photoresist layer, thephotoresist layer is exposed to a desired pattern of radiation. Next,the exposed photoresist layer is developed utilizing a conventionalresist development process. After the development step, an etching stepis performed to transfer the pattern from the patterned photoresistlayer into the template layer 28L utilizing the ARC layer 26L as an etchstop. The etching step used in forming the at least one opening 30comprises a dry etching process, a wet chemical etching process or acombination thereof. Exemplary dry etching processes that can be used inthe present disclosure include, but are not limited to, reactive ionetching (RIE), ion beam etching, plasma etching and laser ablation.Typically, RIE is used to form the at least one opening 30. Aftertransferring the pattern into the template layer 28L, the patternedphotoresist layer can be removed utilizing a conventional resiststripping process such as, for example, ashing. The at least one opening30 exposes at least one portion of the ARC layer 26L. Remaining portionsof the template layer 28L are herein referred to as patterned templatelayer 28.

Referring to FIG. 3, a self-assembly material 32 is deposited in the atleast one opening 30 by casting a solution of the self-assembly materialover the patterned template layer 28. The solution of the self-assemblymaterial 32 can be cast by any suitable technique, such as, for example,spin coating, roll coating, spraying, ink coating or dip coating. Thedeposited self-assembly material typically has a thickness less than orequal to a height of the patterned template layer 28.

The self-assembly material 32 can include any material capable offorming a self-assembled periodic pattern. In some embodiments of thepresent disclosure, the self-assembly material 32 is a block copolymer.Exemplary block copolymers include, but are not limited to,poly(styrene-b-methyl methacrylate), poly(styrene-b-vinyl pyridine),poly(styrene-b-butadiene), poly(styrene-b-isoprene),poly(styrene-b-alkenyl aromatics), poly(isoprene-b-ethylene oxide),poly(styrene-b-(ethylene-propylene)), poly(ethyleneoxide-b-caprolactone), poly(butadiene-b-ethylene oxide),poly(styrene-b-t-butyl (meth)acrylate), poly(methylmethacrylate-b-t-butyl methacrylate), poly(ethylene oxide-b-propyleneoxide), poly(styrene-b-tetrahydrofuran),poly(styrene-b-dimethylsiloxane),poly(styrene-b-ferrocenyldimethylsilane),poly(styrene-b-isoprene-b-ethylene oxide),poly(styrene-b-isoprene-b-methyl methacrylate) andpoly(styrene-b-ferrocendimethylsilane-b-isoprene). In one embodiment,the self-assembly material 32 is poly(styrene-b-methyl methacrylate)(PS-b-PMMA).

Referring to FIG. 4, microphase separation of the self-assembly material32 provides a first self-assembled region 32 a and a secondself-assembled region 32 b. The first and the second self-assembledregions 32 a and 32 b comprise different components of the self-assemblymaterial 32. In one embodiment, when the self-assembly material 32 is ablock copolymer, the first self-assembled region 32 a may contain oneblock of the block copolymer, and the second-assembled region 32 b maycontain a different block of the block copolymer. In some embodiments,the microphase separation of the self-assembly material 32 can befacilitated by annealing. Exemplary annealing processes include, but arenot limited to, thermal annealing, thermal gradient annealing andsolvent vapor annealing. In one embodiment of the present disclosure andas shown in FIG. 4, the microphase separation of the self-assembly layer32 forms a lamellar pattern with the first self-assembled regions 32 aand the second self-assembly 32 b oriented perpendicular to the uppersurface of the ARC layer 26L. In the lamellar pattern, the firstself-assembled region 32 a aligns adjacent to each sidewall of thepatterned template layer 28 and the second self-assembled region 32 b islocated between adjacent first self-assembled regions 32 a.

Referring to FIG. 5, a first pattern 34 can be formed after removing oneof the first self-assembled region 32 a or the second self-assembledregions 32 b. In one embodiment and as shown in FIG. 5, the secondself-assembled region 32 b is removed selectively to the first assembledregion 32 a and the ARC layer 26. The second self-assembled region 32 bcan be removed by a dry etching process or a wet chemical etchingprocess. In one embodiment, an oxygen plasma is performed to remove thesecond self-assembled region 32 b, while leaving the firstself-assembled region 32 a intact. The first pattern 34 exposes at leastone portion of the upper surface of the ARC layer 26L.

Referring to FIG. 6, the first pattern 34 is transferred into theunderlying ARC layer 26L and the OPL layer 24L to provide a secondpattern 36. The first pattern 34 can be transferred utilizing at leastone etch. In this case, the patterned template layer 28 and the firstself-assembled region 32 a serve as an etch mask, and the hardmask layer20L serves as an etch stop. The etch used in forming the second pattern36 may comprise a dry etching process, a wet chemical etching process ora combination thereof. Exemplary dry etching processes include, but arenot limited to, RIE, ion beam etching, plasma etching and laserablation. Remaining portions of the material stack 22 are hereinreferred to as patterned material stack 22′. Within the patternedmaterial stack 22, remaining portions of the ARC layer 26L are hereinreferred to as patterned ARC layer 26, while remaining portions of theOPL 24L are herein referred to as patterned OPL 24.

Referring to FIG. 7, when the second pattern 36 is not properly formed,i.e., it contains defects due to conditions of the etch transfer processand exterior variables, the first self-assembled region 32 a and thepatterned material stack 22′ need to be removed from the substrate 10.The first self-assembled region 32 a can be removed by a dry etchingprocess or a chemical wet etching process. In one embodiment, the firstself-assembled region 32 a is removed by a dry etching process. The drygas includes, but is not limited to, a combination of H₂, N₂, O₂ or Cl₂.Residues 38 of the first-assembled region 32 a may remain on exposedsurfaces of the patterned material stack 22′.

The residues 38 as well as the patterned material stack 22′ (i.e., thepatterned template layer 28, the patterned ARC layer 26 and thepatterned OPL 24) can then be completely removed from the substrate 10by a chemical mechanical polishing (CMP) process. In the CMP process, aflat soft polishing pad is used with a CMP slurry containing abrasiveparticles. In one embodiment, the CMP slurry contains silica abrasiveparticles in an amount from 0.1% to 0.5% by weight with respect to thetotal weight of the CMP slurry. The CMP slurry may have a pH from 6 to10.5. The mechanical pressure used in the CMP process can be from 0.5psi to 2 psi. The CMP process does not affect the underlying hardmasklayer 20L. Thus, the hardmask layer 20L remain on the substrate 10 afterthe CMP process (FIG. 8).

Comparing to the conventional rework process using either dry cleaningor wet chemical cleaning, the CMP process of the present disclosureprovides several advantages. First of all, the CMP process eliminatesthe need for complicated process recipes which are required to removemultiple patterning layers. It also avoids etching related issues thatcan arise from a conventional rework process, such as roughing of theunderlying hardmask layer due to over etching. Moreover, the CMP processis not sensitive to incompatible etch chemistries. Furthermore, bycombining chemical and mechanical forces, the CMP process eliminates theconcern of rework failure due to end-point trace being out ofspecification (e.g., failure due to a dose shift in lithography andetching).

FIGS. 9A and 9B are scanning electron micrograph (SEM) images of thestructure of FIG. 8 before (FIG. 9A) and after (FIG. 9B) the CMPprocess. In one embodiment and as shown in FIG. 9A. a patterned materialstack having a multilayer of patterning layers is formed over a hardmasklayer 20L. The patterned material stack is composed of, from bottom totop, a 135 nm thick patterned OPL 24, a 20 nm thick patterned SiARClayer 26 and a multilayer patterned template layer 28 including a lower50 m thick OPL and an upper 30 nm thick SiARC layer. As shown in FIG.9B, the CMP process removes these pattern transfer layers completelyfrom the upper surface of the hardmask layer 20L and no residues ofthese pattern transfer layers can be observed after the CMP process.

As shown in FIGS. 10-11, the CMP process described above can also beused in a post pattern transfer cleaning process.

Referring to FIG. 10, when the second pattern 36 is properly formed, thesecond pattern 36 can be further transferred into the hardmask layer 20Lto provide a third pattern 42. The etch used to transfer the secondpattern 36 may comprise a dry etching process, a wet chemical etchingprocess or a combination thereof. Typically, RIE is used to transfer thesecond pattern 36 into the hardmask layer 20L. The RIE gas can be acombination of Cl₂, N₂, H₂, O₂ and CH_(x)F_(y). Remaining portions ofthe hardmask layer 20L are herein referred to as patterned hardmasklayer 20.

Referring to FIG. 11, after the second pattern 36 is transferred intothe hardmask layer 20L, the first self-assembled region 32 a can beremoved using the same process as described above in FIG. 7. Residues 44of the first self-assembled region 32 a remain on the exposed surfacesof the patterned material stack 22′ and the patterned hardmask layer 20together with the patterned material stack 22′ can then be completelyremoved from the substrate 10 by the CMP process as described above inFIG. 7. The post CMP cleaning process specifically removes any residuesincluding the residues 44 in the patterned hardmask layer 20, but doesnot affect the patterned hardmask layer 20 (FIG. 12). Thus, as shown inFIG. 12 the patterned hardmask layer 20 remains on the substrate 10after the CMP process.

While the present disclosure has been particularly shown and describedwith respect to various embodiments thereof, it will be understood bythose skilled in the art that the foregoing and other changes in formsand details may be made without departing from the spirit and scope ofthe present disclosure. It is therefore intended that the presentdisclosure not be limited to the exact forms and details described andillustrated, but fall within the scope of the appended claims.

What is claimed is:
 1. A method for making a semiconductor structurecomprising: providing a hardmask layer on an uppermost surface of asubstrate; forming a material stack on the hardmask layer, wherein thematerial stack includes at least one pattern transfer layer and atemplate layer present on the pattern transfer layer; forming at leastone opening in the template layer; forming a patterned structure in theopening, the patterned structure comprising a first self-assembledregion and a second self-assembled region; removing the secondself-assembled region to provide a first pattern, wherein the firstpattern is defined by the first self-assembled region; transferring thefirst pattern into the at least one pattern transfer layer to provide asecond pattern; removing the first self-assembled region; and removingresidues of the first self-assembled region, remaining portions of thetemplate layer, remaining portions of the at least one pattern transferlayer from the substrate by performing a chemical mechanical polishing(CMP) process.
 2. The method of claim 1, wherein the at least onepattern transfer layer comprises an organic planarization layer (OPL)and an antireflective coating (ARC) layer present on the OPL.
 3. Themethod of claim 2, wherein the OPL comprises near-frictionless carbon(NFC) material, diamond-like carbon, polyarylene ether, or polyimide. 4.The method of claim 2, wherein the ARC layer comprises asilicon-containing ARC (SiARC).
 5. The method of claim 1, wherein thetemplate layer is a single layer structure comprising polymethacrylateor polyester.
 6. The method of claim 1, wherein the template layer has amultilayer structure comprising another OPL and another ARC layerpresent on the another OPL.
 7. The method of claim 6, wherein theanother ARC layer comprises a SiARC.
 8. The method of claim 1, whereinthe patterned structure comprises a block copolymer.
 9. The method ofclaim 8, wherein the block coploymer comprises poly(styrene-b-methylmethacrylate), poly(styrene-b-vinyl pyridine),poly(styrene-b-butadiene), poly(styrene-b-isoprene),poly(styrene-b-alkenyl aromatics), poly(isoprene-b-ethylene oxide),poly(styrene-b-(ethylene-propylene)), poly(ethyleneoxide-b-caprolactone), poly(butadiene-b-ethylene oxide),poly(styrene-b-t-butyl (meth)acrylate), poly(methylmethacrylate-b-t-butyl methacrylate), poly(ethylene oxide-b-propyleneoxide), poly(styrene-b-tetrahydrofuran),poly(styrene-b-dimethylsiloxane),poly(styrene-b-ferrocenyldimethylsilane),poly(styrene-b-isoprene-b-ethylene oxide),poly(styrene-b-isoprene-b-methyl methacrylate), orpoly(styrene-b-ferrocendimethylsilane-b-isoprene).
 10. The method ofclaim 1, wherein the hardmask layer comprises oxide, nitride,oxynitride, or a combination thereof.
 11. The method of claim 10,wherein the hardmask layer comprises titanium nitride or silicon oxide.12. The method of claim 1, wherein the performing CMP process comprisesusing a CMP slurry.
 13. The method of claim 12, wherein the CMP slurrycomprises silicon abrasive particles.
 14. The method of claim 12,wherein the CMP slurry has a pH value from 6 to 10.5.
 15. The method ofclaim 1, wherein the performing CMP process is conducted under apressure from 0.5 psi to 2 psi.
 16. The method of claim 1, wherein theforming the at least one opening in the template layer comprises:providing a photoresist layer on a top surface of the template layer;patterning the photoresist layer to define the at least one opening inthe photoresist layer; and transferring the at least one opening intothe template layer.
 17. The method of claim 1, wherein said forming saidpatterned structure comprises: depositing a self-assembly material; andannealing said self-assembly material to cause microphase separation ofsaid self-assembly material.
 18. The method of claim 1, wherein thetransferring the first pattern into the at least one pattern transferlayer is accomplished by a dry etch, a wet chemical etch, or acombination thereof.
 19. The method of claim 1, further comprisingtransferring the second pattern into the hardmask layer prior to theremoving the first self-assembled region.